DRIVERS-3133 Add commitTimestamp to ChangeStreamDocument

source/change-streams/change-streams.md

@@ -227,6 +227,12 @@ class ChangeStreamDocument {
    */
   clusterTime: Timestamp;
 
+  /**
+   * When this operation was committed.
+   * Only present for events in a transaction and only when the `showExpandedEvents` change stream option is enabled.
+   */
+  commitTimestamp: Optional<Timestamp>;
+
 }
 
 class UpdateDescription {
@@ -1026,6 +1032,8 @@ There should be no backwards compatibility concerns.
 
 ## Changelog
 
+- 2026-01-30: Add `commitTimestamp` to `ChangeStreamDocument`.
+
 - 2025-09-08: Clarify resume behavior.
 
 - 2025-03-31: Update for expanded field visibility in server 8.2+

source/change-streams/tests/unified/change-streams-commitTimestamp.yml

@@ -0,0 +1,65 @@
+description: "change-streams-commitTimestamp"
+schemaVersion: "1.7"
+runOnRequirements:
+  - minServerVersion: "8.2.0"
+    topologies: [ replicaset, sharded ]
+    serverless: forbid
+
+createEntities:
+  - client:
+      id: &client0 client0
+  - database:
+      id: &database0 database0
+      client: *client0
+      databaseName: *database0
+  - collection:
+      id: &collection0 collection0
+      database: *database0
+      collectionName: *collection0
+  - session:
+      id: &session0 session0
+      client: *client0
+
+initialData:
+  - collectionName: *collection0
+    databaseName: *database0
+    documents: []
+
+tests:
+  - description: "when showExpandedEvents is true, commitTimestamp is included for operations in a transaction"
+    operations:
+      - name: createChangeStream
+        object: *collection0
+        arguments:
+          pipeline: []
+          showExpandedEvents: true
+        saveResultAsEntity: &changeStream0 changeStream0
+      - name: startTransaction
+        object: *session0
+      - name: insertOne
+        object: *collection0
+        arguments:
+          document: { x: 1 }
+          session: *session0
+      - name: commitTransaction
+        object: *session0
+      - name: iterateUntilDocumentOrError
+        object: *changeStream0
+        expectResult:
+          operationType: insert
+          ns:
+            db: *database0
+            coll: *collection0
+          commitTimestamp: { $$exists: true }
+      - name: insertOne
+        object: *collection0
+        arguments:
+          document: { x: 1 }
+      - name: iterateUntilDocumentOrError
+        object: *changeStream0
+        expectResult:
+          operationType: insert
+          ns:
+            db: *database0
+            coll: *collection0
+          commitTimestamp: { $$exists: false }